IBM 3741 Data Station Reference Manual page 95

LINE TERMINATION AND ERROR CONDITIONS
The following sections describe line termination of a call,
BSCA error conditions and indicators, and BSCA disk
errors that can occur during teleprocessing, and what the
disk address and the record displayed mean when a tele-
processing error occurs. The section, Error Recovery
Procedures, provides information on how the operator can
restart the communications mode when an error stops the
teleprocessing.
Termination of the Data Call
On switched lines: a data call is terminated when a discon-
nect sequence is received, when a disconnect timeout occurs,
or when RESET is pressed. Pressing RESET takes the 3741
out of a communications mode of operation. The end of
data and end of extent are updated (see Figure 37 or 39)
under the following conditions:
• if a disconnect sequence is received and either:
1. The mode is R, RC, BT, BC, OT,
~C,
KC, or KT.
2.
The mode is RJ, BJ, KJ, or OJ; and a disk full
error has occurred.
• If a disconnect timeout has occurred and either:
1. The mode is R, RC, BT, BC, OT,
~C,
KC, or KT.
2. The mode is RJ, BJ, KJ, or OJ; and a disk full
error has occurred.
If the mode is T, P, R, B, 0, J, KT, BT, or OT, the disk is
positioned at the original position before transmission or
reception took place, and the modem is conditioned to
automatically answer a telephone call if it is in an auto
answer mode. If the mode is TT, TI, PT, PI, RC, RJ, BI,
BJ, BC, 01, OJ, DC, JT, JI, KC, KI, or KJ, the modem is
not conditioned to answer a telephone call.
Transparency Check (T)
This error condition occurs when the 3741 is in a transmit
(J, T) or a transmit/receive, (B, K) mode, and one of the
following characters is read from disk: SYN, EOT, OLE,
NAK, ENQ, ETB, ETX, ITB, STX, or SOH. The 3741
sends ENQ in place of the data link control character,
and then follows the response with an EOT. This error
also occurs when the 3741 with expanded communications
is in the J or K mode, and an I RS or I FS character is read
from disk. The 3741 sends ENQ in place of the data link
control character, and then follows the response with an
EOT.
Line Check (C)
A line check occurs when seven receive timeouts or 15 line
bid timeouts on a switch network have occurred during the
transmitting or receiving of data. If the 3741 is on
switched lines, it disconnects from the line. If the terminal
is on nonswitched lines, it goes into a control mode, moni-
toring the line for line bids.
Remote Abort (R)
A remote abort occurs when an EOT or a disconnect
sequence is received as a response to a data transmission
block, or following a response sent after receiving a data
transmission block that did not end with ETX.
On nonswitched or switched lines, an EOT causes the
3741 to go into control mode, monitoring for line bids.
On switched lines, a disconnect sequence or a disconnect
timeout causes the 3741 to disconnect from the telephone
line.
Message Aborted (a)
A message aborted c()ndition occurs after four consecutive
negative responses have been received as responses to the
same data transmission block. The 3741 sends an EOT
Inquiry Mode Termination following the fourth negative response.
The operator can terminate inquiry mode by pressing FUNCT
SEL lower and RETURN TO INDEX, thus causing the data Received Line Bid (V)
set label in position 00008 to be displayed.
BSCA Error Conditions and
r
ndications
Characters in parentheses indicate what is displayed in the
error indicator position of the display's status line.
When the 3741 receives a line bid while in one of the follow-
ing point-to-point communications modes; RC, TT, PT, BC,
~C,
JT, KC, RJ, BJ, TI, BI, 01, P.I, JJ, KJ, or KI, the 3741
responds with a negative response (NAK) and gives a received
line bid indication.
Communications 89